Nice to meet you all here in these forums. I want to ask something. I know that in order to sell a game you must have a license or something like that from the company that made the game engine. Is this engine free (Crystal Space)? Can i sell the game that i will make with this engine?

You can make commercial games using CS provided that you comply to the LGPL license. You can read about this license in the CS source distribution (file 'LICENSE'). But in short you can make your own game and keep your own sources closed. However, any modification you do to the CS engine you have to make public.